docs: def _set_current(self, new_current):
          """
          Change the current default prefix, for internal usage
  
          Args:
              new_current(str): Name of the new current prefix, it must already
                  exist
  
          Returns:
              None
  
          Raises:
              PrefixNotFound: if the given prefix name does not exist in the
                  workdir
          """
          new_cur_full_path = self.join(new_current)
          if not os.path.exists(new_cur_full_path):
              raise PrefixNotFound(
                  'Prefix "%s" does not exist in workdir %s' %
                  (new_current, self.path)
              )
  
          if os.path.lexists(self.join('current')):
              os.unlink(self.join('current'))
  
          os.symlink(new_current, self.join('current'))
          self.current = new_current